1. Field of the Invention
The invention relates generally to an apparatus for converting solar energy into a usable energy product and, more particularly, to an economical system for converting a high percentage of sunlight radiant energy to electricity with negligible optical losses utilizing thermophotovoltaic cells. The system simultaneously produces both AC and DC electricity on a sustainable cycle with zero carbon emission.
2. Description of Related Art
Solar energy has been available as a source of power for more than 4.5 billion years. For centuries, inventors have been devising various means to harness this energy. As far back as the third century B.C., records indicate that the Greek and Roman armies used “burning mirrors” to focus sunlight as weapons of war to ignite fires and to burn sails of enemy warships.
Solar energy provides the world either directly or indirectly with the majority of its energy. Solar energy is a renewable energy source having vast potential. Although solar energy is abundant, a major drawback is that it is diffuse and not available at all hours. Solar energy can be affected by the time of the day, the seasons, and the changing sun path in the sky as the earth's axis is not at a right angle to the sun but it is tilted away at an angle of 23.5°.
For decades, inventors have tried various systems for harnessing this incredible energy source. For example, U.S. Pat. Nos. 3,988,166; 4,286,581; 5,275,149 and 4,038,971 have sought to control and convert this energy into a cost-effective usable form. Unfortunately, these systems are cumbersome, expensive to manufacture and maintain, expensive to operate, and yield little in terms of usable, convertible energy.
The article entitled “Principles of Solar Thermal Conversion” by R. H. B. Exell, 2000. King Mongkut's University of Technology Thonburi also discusses, in terms of academic interest only, of trapping solar radiation in an enclosed volume with perfectly reflecting walls at the temperature of the sun, i.e., approximately 5800 K and the need for a parabolic concentrator that focuses direct solar radiation into the enclosed volume. The article further discusses that if solar energy were to be used on a large scale, since solar energy is theoretically a very high temperature resource, one should try to harness it at this very high temperature for efficient conversion and then use the waste heat for low temperature purposes instead of downgrading the solar energy with low temperature collectors at the start. This article recites a theory for what is desired in this technology, but provides no direction as to how it can be achieved.
U.S. Pat. No. 7,640,931 to Tarabishi (hereinafter, “the '931 patent”), the entirety thereof being incorporated by reference thereto, is directed to a solar collecting system which can concentrate or condense solar energy at a fixed, stationary focal point to economically harness the sun's energy into a manageable and convertible form as desired in the Exell article. In particular, the '931 patent teaches a system for tracking the sun and maintaining a constant fixed focal point or sub-focal point to at least partially condense the sun's rays into a high-energy beam that can be redirected to a predetermined location for generating electrical power, heat energy, steam, and the like.
U.S. Pat. No. 8,413,442, also to Tarabishi (hereinafter, the '442 patent”), the entirety thereof being incorporated by reference thereto, is directed to an economical system for harnessing the sun's energy collected from the system described in the '931 patent, storing this energy, and/or converting this energy into a mechanical and/or electrical energy product on a sustainable cycle. The system utilizes one or more enclosed volume chambers having a mirrored inner surface connected in series for trapping the heat therein, a source for feeding a first fluid into the chamber to convert this fluid into a high pressure source, an outlet for allowing the high pressure source to exit the chamber, and at least one turbine for converting the high pressure source into mechanical and electrical energy product. The enclosed volume chambers may or may not include a heat absorbing member located therein for trapping and storing the energy for use during sunless hours. The heat trapped within the chamber can reach a temperature as high as plasma level. The system is highly efficient in that it achieves almost 100% conversion of the solar energy into a usable format and has increased efficiency through the use of multiple integrated units which are compact in size and space compared to previously used systems.
Photovoltaic cells are used to convert light into electricity. Thermophotovoltaic cells use different technology to produce electricity. “Thermo” means heat and therefore these cells convert heat into electricity. Thermophotovoltaic cells use semiconductors, which are designed for specific wavelength, invisible light, like infrared rays, released by hot objects. This way of generating electricity is very neat and clean. Another advantage to the use of thermophotovoltaic cells is that they do not require much maintenance to work and do not produce any by-product that can harm the environment. For this reason, thermophotovoltaic cells are “clean” sources of energy.
The article entitled “Utilization of the Wider Solar Spectrum Using Thermophotovoltaic Cells” by Dr. Dino Ponnampalam recognizes that thermophotovoltaic cell technology may be a way to harness solar energy without actually utilizing direct sunlight to meet the ever-increasing demand for energy without depleting the earth's natural resources. Since thermophotovoltaic cell systems match the band gap in the near infrared (0.078-3 micrometers), whereas the sun emits radiation that spans the entire electromagnetic (EM) spectrum, an interesting point to note is that the majority of the sun's irradiance is in the infrared region, making exploitation of this region, and this technology extremely worthwhile. As noted by Dr. Ponnampalam, the drawback of efficiency conversion of thermophotovoltaic cell technology has prevented a roll out of this technology. Dr. Ponnampalam further notes that currently there is no single piece of solar energy technology that could fully harness the power of the sun in providing and sustaining the power demands of society; however, through the intelligent utilization of the technology available, it is indeed feasible that solar energy could meet the energy demands of the world.
The present invention is directed to a system that utilizes thermophotovoltaic cell technology in an efficient and cost-effective manner. The system is capable of converting up to 95% of sunlight radiant energy to electricity simultaneously producing AC and DC energy using the proper level of condensed solar energy temperature. The system uses the power of simplicity to exploit the broad spectrum of the harnessed solar energy resulting from the design of the '931 patent and uses it in a creative way. The system of the present invention is self-sustaining, achieving a powerful AC and DC electricity combined output with the highest energy intensity per space unit, allowing the highest conversion of sunlight energy across the entire spectrum to electricity at zero carbon emission. Additionally, the present invention utilizes a creative way that relies upon a combination of diverse frequencies of thermophotovoltaic cells to generate DC electricity and, from waste heat to generate AC electricity, as well as from direct condensed solar beams to also generate AC electricity all from the same source of solar energy, and is capable of storing energy for several weeks, all in a single system. A full implementation of all of the system stages would result in a cost of kwh of less than one cent, making carbon capture and storage affordable.